1/*
2 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 */
5
6#include <signal.h>
7#include <kern_util.h>
8#include <longjmp.h>
9#include <sysdep/ptrace.h>
10#include <generated/asm-offsets.h>
11
12/* Set during early boot */
13static int host_has_cmov = 1;
14static jmp_buf cmov_test_return;
15
16static void cmov_sigill_test_handler(int sig)
17{
18 host_has_cmov = 0;
19 longjmp(cmov_test_return, 1);
20}
21
22void arch_check_bugs(void)
23{
24 struct sigaction old, new;
25
26 printk(UM_KERN_INFO "Checking for host processor cmov support...");
27 new.sa_handler = cmov_sigill_test_handler;
28
29 /* Make sure that SIGILL is enabled after the handler longjmps back */
30 new.sa_flags = SA_NODEFER;
31 sigemptyset(&new.sa_mask);
32 sigaction(SIGILL, &new, &old);
33
34 if (setjmp(cmov_test_return) == 0) {
35 unsigned long foo = 0;
36 __asm__ __volatile__("cmovz %0, %1" : "=r" (foo) : "0" (foo));
37 printk(UM_KERN_CONT "Yes\n");
38 } else
39 printk(UM_KERN_CONT "No\n");
40
41 sigaction(SIGILL, &old, &new);
42}
43
44void arch_examine_signal(int sig, struct uml_pt_regs *regs)
45{
46 unsigned char tmp[2];
47
48 /*
49 * This is testing for a cmov (0x0f 0x4x) instruction causing a
50 * SIGILL in init.
51 */
52 if ((sig != SIGILL) || (get_current_pid() != 1))
53 return;
54
55 if (copy_from_user_proc(tmp, (void *) UPT_IP(regs), 2)) {
56 printk(UM_KERN_ERR "SIGILL in init, could not read "
57 "instructions!\n");
58 return;
59 }
60
61 if ((tmp[0] != 0x0f) || ((tmp[1] & 0xf0) != 0x40))
62 return;
63
64 if (host_has_cmov == 0)
65 printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
66 "processor doesn't implement. Boot a filesystem "
67 "compiled for older processors");
68 else if (host_has_cmov == 1)
69 printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
70 "processor claims to implement");
71 else
72 printk(UM_KERN_ERR "Bad value for host_has_cmov (%d)",
73 host_has_cmov);
74}
75

source code of linux/arch/x86/um/bugs_32.c